The bson package

A BSON Document is an untyped (dynamically type-checked) record.
I.e. it is a list of name-value pairs, where a Value is a single
sum type with constructors for basic types (Bool, Int, Float,
String, and Time), compound types (List, and (embedded) Document),
and special types (Binary, Javascript, ObjectId, RegEx, and a few
others).
A BSON Document is serialized to a standard binary encoding
defined at http://bsonspec.org. This implements version 1 of
that spec.